Target Healing--

Hey guys,

New to the priest class and one thing that I wanted to inquire about is that I've seen several PVE raiding vid's and I saw a few people with there UI set up in a way where you don't have to click the target to heal it. They were just able to scroll over there target frame and heal them with out loosing focus on there current target, is this done via UI or with macros? and if so, what are they? thank you!!